John:
Big guy to big guy, and angler to angler, I wouldn't worry about insulation--just buy them big enough to add insulation underneath. I'm on my second pair of Patagonia breathables. Pricy, but their customer support is outstanding, and I got three years out of the first pair, hunting and fishing pretty much year-round, before I even had to deal with pin hole leaks along the seams, and then was able to get another year+ of good service with a little Aquaseal touch up.
My current pair are near the end of year 2 with no sign of any issues. I don't baby them--I hunt and fish the salt, sit on sharp rocks, rub against barnacles, etc.
I wear just fleece pants under mine until it's below freezing, then add 1 or 2 layers of poly pro long johns. With 2 layers of poly and heavy fleece pants, they are still comfortable to walk in, though I look like a very large Michelin man. I've hunted right to the end of the season every year, and stayed as comfortable as can be expected standing in the mud at near zero.
As you know, folks rave about Simms durability, too.
Every time I've tried to save money with less expensive waders, I've ended up wet or only getting a season or so out of them.